The present invention relates to a latch mechanism, in particular, although not exclusively, to a latch mechanism for use on a door of a motor vehicle.
It is known for an intended passenger of a locked motor vehicle to try to gain access to the motor vehicle by operating (lifting) an outer passenger door handle before all the doors of the motor vehicle are unlocked by an intended driver with a key actuating a central door locking system. With some models of motor vehicle, the action the intended passenger takes in operating the door handle prevents the latch mechanism of that door from being unlocked as the other doors are unlocked by the central door locking system.
Recently it has been known to provide a latch mechanism which when an associated outside door handle is lifted whilst a central door locking system unlocks the other doors of the motor vehicle and the outside door handle is subsequently released, the latch mechanism automatically moves to an unlocked condition. Such unlocking is known as xe2x80x9cpanic unlockingxe2x80x9d.
Latch mechanisms which provide for panic unlocking included additional components when compared to latch mechanisms which do not have such a panic unlocking facility.
An aim of the invention is to provide a xe2x80x9cpanic unlockingxe2x80x9d type of latch mechanism having a reduced number of parts.
According to a first aspect of the invention there is provided a latch mechanism including a latch bolt having an open position for releasing a striker in use, and a closed position for retaining a striker in use, and a pawl having a retaining position for retaining the latch bolt in at least its closed position, and a release position for allowing the latch bolt to move between its open and closed positions, a release element having a rest position and an actuated position, a release link having an engaging position and a disengaged position, movement of the release element between its rest position and its activated position causing movement of the release link, movement of the release element from the rest position to the actuated position when the release link is in its engaging position causing the pawl to move to its release position, and movement of the release element from the rest position to the actuated position when the release link is in its disengaged position allowing the pawl to remain in its retaining position, and a locking member having a locked position, wherein the release link is held in its disengaged position and an unlocked position allowing the release link to move to its engaging position, characterised in that a biasing means is provided which provides a bias action force and a bias reaction force, the action force acting to bias the release link towards its engaging position and the bias reaction force acting to bias the latch bolt towards its open position.
In that way, a single biasing means can act to bias both the release link and the latch bolt. The biasing means is preferably a spring. In one form the spring is a torsion spring, most preferably having two arms.
In one embodiment of the invention, a first arm act on the latch bolt and a second arm acts on the release link. An abutment surface is preferably provided on the latch bolt against which the first arm acts. Preferably the release link has a transverse arm upon which the biasing means acts. Such an arrangement gives rise to a turning moment on the release link. Preferably one or more of the latch bolt, pawl, release element, release link and locking lever are pivotally mounted. Preferably the latch bolt and the release element share a first common pivot. Preferably the spring body is mounted on the first common pivot. With the axis of the spring body fixed, the forces through the arms tend toward equalisation. Preferably the transverse arm is fixed to the second arm of the spring. Preferably the release element and the release link share a second common pivot. Preferably the bias action force acts between the first common pivot and the second common pivot.
According to a further aspect of the invention there is provided a motor vehicle having a latch mechanism in accordance with the first aspect of the invention or any of the consistory clauses relating thereto.
These and other features of the present invention will be best understood from the following specification and drawings.